1. Field
The invention is in the field of immunology, and more specifically, in the field of treating immune systems to reduce the chance of the system attacking beneficial cells. This includes treatments and procedures for reducing the risk of graft versus host disease associated with bone marrow transplantation, diseases associated with organ or other tissue transplants, as well as autoimmune diseases.
2. State of the Art
The cellular immune system in animals, particularly mammals such as human beings, include cells in the blood, such as T-cells, which recognize aberrant cells in the body and attack and destroy such cells. Aberrant cells result, for example, from viral and other infections and cancerous and diseased cells and express one or more abnormal antigens. The aberrant cells are recognized by immune system cells. By recognizing and destroying aberrant cells, a body""s cellular immune system kills diseased and other harmful cells and protects the body. However, in some instances (i.e., autoimmune diseases) certain immune system cells attack normal cells. In other instances, such as allogenic bone marrow transplantation, immune system cells attack host cells.
With some cancers, such as leukemia, control of the cancer can only be achieved by treatments such as irradiation or chemotherapy which inadvertently destroy the blood forming cells in the body along with the cancer cells. Bone marrow transplants are done to replace blood forming cells in the body that are destroyed as a result of such treatment. Hematopoietic stem cells are trans-planted into the body to form a new immune system. T-cells are part of traditional bone marrow transplants and, since they came from a donor, recognize the host tissue as being foreign, i.e., aberrant, and develop an immune reaction to the antigens on the host cells. This is generally referred to as graft versus host disease (GVHD). Immunosuppressive drugs are used to reduce GVHD. The two main immunosuppressive drugs used over the last two decades are methotrexate and cyclosporin. Although these drugs used alone or in combination decrease the incidence of GVHD, an unacceptable number of patients still die, R. Storb, Transplantation Proceedings, Vol. 27, #5 (October), 1995, pp. 2653-2656. Attempts have been made to prevent GVHD by the removal of T-cells from the donor inoculum with monoclonal antibodies, lectins, or complement lysis so that only stem cells are transplanted. These methods generally reduce the number of T-cells by 1-3 logs and show significant reductions in acute and possibly chronic GVHD. However, since the host is left without a mature cellular immune system for several weeks while the stem cells develop into a new immune system, the success in reducing GVHD is generally associated with an increased risk of infection and relapse of the original malignancy. In addition, secondary tumors such as Epstein-Barr lymphoproliferative disease are likely to appear, C. Anasetti et al., Annu. Rev. Med. 1995, 46:169-179. It is believed that the increased rate of relapse of the original malignancy and possibly the occurrence of secondary tumors is a result of incomplete destruction of the original malignant cells during treatment. The new immune system which develops from the transplant does not recognize the malignant cells as aberrant and thus does not mount an attack. As a result, the few malignant cells that survive treatment are left to grow unchecked by the new immune system. All of these disorders invariably result in death and no improvement in survival rate has yet been realized for patients given T-cell depleted marrow.
With organ or other tissue transplants made into a body having a cellular immune system, the transplant presents foreign tissue to the body. The cellular immune system, recognizing the tissue as made up of foreign or aberrant cells, attacks the transplanted tissue resulting in what is commonly referred to as transplant rejection where the body rejects the transplant. This is also referred to as host versus graft disease (HVGD). Again, in most transplant cases, immunosuppressive drugs are used to inhibit the body""s attack on and rejection of the transplant. Since the transplant was probably necessary to save the recipient""s life, rejection of the transplant usually results in death. However, use of immunosuppressive drugs to prevent rejection of the transplant generally reduces the ability of the immune system to attack unwanted disease or other harmful cells so the risk of death from disease and infection is increased.
With autoimmune diseases, such as multiple sclerosis, something abnormal happens to a body""s cellular immune system and the immune system attacks and destroys the body""s own cells. This generally results in death unless the immune system""s attack on the body can be controlled. Often, such attacks can be controlled by use of immunosuppressive drugs, however, the success of such control depends upon the disease and the individual. Also, as indicated, use of immunosuppressive drugs reduces the body""s ability to fight disease and infection.
According to the invention, the risk of disease resulting from mononuclear cells in a body attacking normal or grafted cellular antigens (desirable cellular antigens) in the body, such as graft versus host disease (GVHD) or host versus graft disease (HVGD), or some autoimmune diseases, can be significantly decreased by reducing the number of mononuclear cells in the blood in the body that show a tendency to attack the normal or grafted cells. This is done by removing such cells by obtaining cellular antigens from normal or grafted cells likely to be attacked in the body and reacting, in vitro, mononuclear cells to be infused into the body with such normal or grafted cellular antigens. The cytotoxic mononuclear cells, i.e., the cells that would tend to attack such antigens in the body, bind to these cellular antigens. The cells that do not bind to the antigens, i.e., the cells that generally will not attack cells in the body having such antigens, are recovered and infused into the body. The mononuclear cells may be obtained from a donor with the recovered cells being injected into the body of a host, or the mononuclear cells may be withdrawn from the body such as by withdrawing blood from the body, reacted with the antigens, and then infused back into the body. When extracted and reinfused into the body, the procedure can be done in a manner to treat substantially the entire body""s blood supply.
In connection with bone marrow transplants, the risk of graft versus host disease and the chance of infection and relapse of malignancy or secondary tumors can be reduced by a combination of depleting the T-cells in the transplant inoculum and infusing selected donor T-cells into the host to replace the depleted T-cells but reduce the number of T-cells that tend to cause GVHD. The selected and infused donor T-cells boost and maintain the host""s immune system while the host""s hematopoietic system develops from the graft and provide continuing protection against relapse of the original malignancy. The T-cells for infusion into the host are selected by the selective removal from donor mononuclear cells, such as donor peripheral blood cells, of cytotoxic T-cells, such as CD8+ cells, which attack normal host tissue. The cytotoxic T-cells which attack tumor cells and virally or otherwise infected cells remain and can be amplified in number before infusion into the host. The selective removal is accomplished by incubating the donor mononuclear cells with cell derived antigens from the host that are recognized by donor T-cells included in the donor mononuclear cells and recovering the cells that do not attach to the antigens. In a preferred embodiment of the invention the antigens are provided by host fibroblast cells attached in a monolayer to a substrate. The donor cells are passed over the host fibroblasts and the mononuclear cells that do not adhere to the fibroblast are recovered. The selective removal step, sometimes referred to herein as panning, may be repeated several times, with the recovered cells amplified in number each time, if desired, until only a small percentage of cells adhere to the fibroblast. These selected cells are then amplified in number and infused into the host.
If desired to increase the cellular activity in infused cells against the original malignancy in the host, the mononuclear cells from the donor may be activated against the original malignancy in the host prior to selection. This activation step involves culturing the donor mononuclear cells with cell derived antigens from malignant cells from the host. Since the malignant cells also have the body""s normal antigens, the activation step will result in increased numbers of both cells which tend to attack the normal body cells as well as cells which tend to attack the original malignancy. However, the selection or panning step reduces the number of cells which attack the normal cells while leaving the increased number of cells to attack the original malignancy. If this is done, the selection not only reduces the T-cells likely to cause GVHD but also concentrates the T-cells likely to prevent malignancy relapse.
While it is currently preferred with bone marrow transplants to treat blood cells from the donor and then infuse such cells into the host in coordination with the bone marrow transplant using T-cell depleted inoculum, a host""s blood can be treated after the transplant, possibly waiting until signs of GVHD appear. In such cases, host fibroblast cells are obtained from the host either before or after treatment and attached to a substrate. The host""s blood is drawn continuously and the white blood cells separated as in leukophoresis, and the blood returned to the body. This would continue for a period of time to separate substantially all white cells from the blood in the body. The separated white cells are selected or panned by passing them over the fibroblast cells and those that pass over the fibroblast cells are infused back into the body. In this way, the cells causing the GVHD in the body are removed from the body to substantially lessen the chance of GVHD while the remaining cells which attack disease, infection, and the original malignant cells are returned to the body to maintain its immune system and fight relapse of the original malignancy.
Treatment of hosts receiving organ or other tissue transplants would be similar to treatment of a bone marrow transplant host after the transplant takes place in that the blood of the host is withdrawn on a continuing circulation basis with white cells separated therefrom. These white cells are passed over fibroblast cells obtained from the organ or other tissue transplanted into the host or to be transplanted into the host. The cells that pass over such fibroblasts are infused back into the body. In this way, the host cells likely to attack the foreign engrafted tissue are removed from the host, leaving the host with cells to attack other foreign tissue or abnormal cells in normal manner to prevent disease and infection.
Treatment of bodies suffering autoimmune diseases would be similar using normal cells, e.g., fibroblasts, from the body to remove the lympocytes likely to attack such normal tissue.